A message left with National Right to Life asking whether the group seeks to deter Nelson from running again was not immediately returned.
Anti-abortion groups vow to fight Ben Nelson's reelection
Republican leaders in the Senate have reportedly asked Nebraska Gov. Dave Heineman (R) to consider entering the race, which would all but ensure a Republican victory in 2012. And Crossroads GPS, a conservative outside group, is spending one-half million dollars in television ads attacking Nelson.